(i) Technical Field
The present invention relates to an image forming apparatus.
(ii) Related Art
When color registration is performed, a recording material goes to waste in order to determine whether misregistration between toner images of different colors has occurred on the recording material. In particular, in the case where a continuous sheet is used as a recording material, a large portion of the recording material will go to waste. Accordingly, in order to reduce the amount of waste produced when color registration is performed, it has been proposed to stop transportation of a recording material and perform color registration on an intermediate transfer body. However, when the transportation is stopped, a second transfer roller and the like are separated from the intermediate transfer body, and thus, there is a change in the load applied to the moving intermediate transfer body. As a result, the movement speed of the intermediate transfer body changes between when image formation in which a recording material is transported is performed and when color registration in which transportation of a recording material is stopped is performed, and there is a possibility that misregistration will occur when image formation is performed.
In an image forming apparatus that employs a tandem system and directly transfers toner images onto a recording material, it has been proposed to separate a transfer roller of an image engine corresponding to a color that will not be used from a recording material or a transport belt when changing the number of colors to be used. However, similar to the above, there is a possibility that the movement speed of a recording material or the like will change between when the transfer roller is in contact with the recording material or the like and when the transfer roller is separated from the recording material or the like, which in turn results in misregistration.
In other words, in the case where an image forming apparatus in which images are formed and sequentially transferred onto a movable body in such a manner as to be superposed with one another by plural image forming units includes a contact and separation unit that comes into and out of contact with the movable body, there is a possibility of misregistration. Although an image forming apparatus that employs an electrophotographic system has been described above as an example, there is a possibility of misregistration also in an image forming apparatus that employs, for example, an ink-jet system when the image forming apparatus includes a contact and separation unit.